Stabilization of heavy oil fly ash (HFO) for construction and environmental purposes

This work aims to investigate the stabilization of heavy oil fly ash (HFO) using a geopolymerization technique. The stabilization technique entails adding HFO as the filler material to a geopolymer matrix derived from metakaolin. Weight ratio of 20% - compared with the powder precursor (metakaolin) - were added to the metakaolin-based geopolymer. XRD analysis showed that the HFO-based geopolymer comprised two amorphous phases: gel and HFO particles. The HFO-based geopolymer cement exhibited a flexural strength of 7.5MPa, and compressive strength of 31MPa and 28MPa, respectively under dry and immersed conditions. The geopolymer produced featured relatively low density, 1.34 g/cm³, and reasonable water absorption, 18% (w/w), compared with other cement-based materials. A leaching test showed that the HFO toxic metals, such as Ni, Cr, Cu, and Pb, are effectively immobilized in the geopolymer matrix and exhibit concentrations significantly lower than those of HFO powder. The general evaluation of the geopolymer cement produced from metakaolin and HFO particles indicates its potential for a number of applications, including “green” construction materials.